In the art and technology of inkjet printing generally, various metallic and insulating materials have been used in the fabrication of the orifice or nozzle plate of the inkjet pen which controls the ink drop ejection pattern size, geometry and drop volume of ink ejected during the operation of an inkjet pen. In the more specific field of thermal inkjet printing, this pen is frequently provided with a thin film resistor type printhead, and the orifice or nozzle plate becomes the integral and "output" layer of this printhead structure. Nickel or gold plated nickel is a metal frequently used in the manufacture of thermal inkjet printhead orifice plates, and these types of orifice plates are described, for example, in U.S. Pat. No. 4,716,423 issued to C. S. Chan et al and also in U.S. Pat. No. 4,675,083 issued to James G. Bearss et al. The use of a plastic material for an inkjet printhead orifice plate is described, for example, in U.S. Pat. No. 4,829,319 issued to C. S. Chan et al. All of the above identified patents are assigned to the present assignee and are all incorporated herein by reference.
In the manufacture of thermal inkjet printheads of the type wherein thin film resistor substrates have been employed, one common fabrication procedure has been to photolithographically define and electrically interconnect a plurality of heater resistors, such as those made of tantalum aluminum, on a thin film substrate. The base or main support member for the thin film substrate is typically glass (quartz) or silicon upon which a first silicon dioxide, SiO.sub.2, passivation layer is formed and further upon which a tantalum aluminum resistive layer is deposited on the SiO.sub.2 layer to serve as the resistive heater material for the inkjet printhead structure. Conductive trace material such as fine linewidth aluminum patterns are then laid down on top of the tantalum aluminum resistive layer to define the width and length dimensions of the individual heater resistors. These heater resistors are then passivated and protected by the deposition of a suitable passivation layer such as silicon nitride or silicon carbide or a combination or composite of these two dielectric materials.
Continuing the above process, it has been a common practice to construct a so-called barrier layer on top of the above Si.sub.3 N.sub.4 /SiC passivation and protection layer and then photolithographically define therein the firing chamber walls of the barrier layer which are normally concentrically aligned with the previously defined heater resistors. This barrier layer has been typically constructed of a material, such as polyimide or VACREL, and these ink firing chambers in the VACREL are fluidically connected to a source of ink supply and fed by one or more compartments within the main housing of the disposable inkjet pen. To complete the above pen structure, a metal orifice plate typically fabricated of gold plated nickel is then carefully aligned and secured to the exposed surface of the barrier layer so that nozzle openings in the orifice plate are aligned with respect to the center lines of the firing chambers and the centers of each individual heater resistor. This process is generally well known in the art and is described in more detail, for example, in the Hewlett Packard Journal, Volume 16, No. 5, May 1985, incorporated herein by reference. This type of pen body construction is also used in Hewlett Packard's well known and commercially successful ThinkJet, PaintJet, and DeskJet thermal inkjet printers.
Whereas the above type of thin film resistor printhead structure and process of manufacture have been highly regarded and widely accepted and used in the production of Hewlett Packard's disposable thermal inkjet pens, the fabrication process for making these thin film printheads is relatively expensive and is somewhat complex in both the overall number of process steps required and also in the requirement for handling and treating diverse type metal and insulating materials in the printhead manufacturing process. For example, since metal orifice plate fabrication and plating assembly lines have to be maintained separate and apart from the other thin film processing stations where the thin film resistor substrate and overlying barrier layers were processed, the required large number of individual processing steps not only had an adverse effect on achievable process yields, but they also increased significantly the overall manufacturing costs of the disposable pens in which these printheads were used.